[ 291 J 



LV. Account ef a Series of Experiments, showing the 

 Effects of Compression in modifying the Action of Hc^at. 

 Bij Sir James Hall, Bart. F.R.S. Edin. 



[Continufd from p. SC3.] 



IV. Experiments in Gun-Barrels resumed. — The Vertical 

 Apparatus applied to them. — Barrels bored in solid Bars. 

 — Old Sable Iron. — Fusion of the Carbonate of Livie. — 

 Its Action on Porcelain. — Additional Apparatus required 

 in consequence of that Action. — Good Results ; in parti- 

 cular, four Experiments illustiafing the Theonj of In- 

 ternal Calcination, and showing the Efficacy of the Car- 

 bonic Acid as a Flux. 



Since I found that, with porcelain tubes, I could neither 

 confine the carbonic acid entirely, nor expose the carbonate 

 in them to strong heats, I at last determined to lay them 

 aside, and return to barrels of iron, with which I had for- 

 merly obtained some good results, favoured, perhaps, by 

 some accidental circumstances. 



On the 12th of February 1803, I began a series, of expe- 

 riments with gun-barrels, resuming my former method of 

 working with the fusible metal, and with lead; but altering 

 the position of the barrel from horizontal to vertical, the 

 breech beino^ placed upwards during the action of heat on 

 the carbonate. This very simple improvement has been pro- 

 ductive of advantages no less remarkable than in the case of 

 the tubes of porcelain. In this new position, the included 

 air, quitting the air tube on the fusion of the metal, and 

 rising to the breech, is exposed to* the greatest heat of the 

 furnace, and muse therefore re-act with its greatest force ; 

 whereas, in the horizontal position, that air might go ai far 

 back as the fusion of the metal reached, where its elasticity 

 would be much feebler. The same disposition enabled me 

 to keep the muzzle of the barrel plunged, during the action 

 of heat, in a vessel filled wih water; which contributed 

 very much both to the convenience and safety of tliese ex- 

 periments. 



In this view, making use of the brick furnace with the 

 T 2 vertical 



